Attachment characteristic of indigenous acidophilic bacteria to pyrite surface in mine waste

Abstract

Indigenous acidophilic bacteria living in a hot acidic spring near Hatchobaru thermal electricity plant in Japan were incubated and used for the bioleaching experiment. The indigenous acidophilic bacteria grew properly in the leaching (sulfur-rich) solution and, over the course of incubation, the pH decreased and Eh increased. In relation to the bacterial growth-curve, the lag phase was hardly shown while the exponential phase was significantly fast. Following Gram staining of the bacteria, they were categorized into Gram-negative and Gram-positive. When the bacteria were inoculated to pyrite, rod-shaped bacteria and round-shaped microbes were well attached to the surface of the pyrite. The size of the rod-shaped bacteria ranged from 1.05–1.10 μm to 4.01–5.38 μm. Round-shaped microbes were more than 3.0 μm in diameter. Paired cells of rod-shaped bacteria were linearly attached to the surface of the pyrite. The round-shaped microbes showed strong organic attachment. Twenty days after the indigenous acidophilic bacteria were inoculated to a pyrite-leaching medium, the bacterial sample had a greater concentration of Fe and Zn than within the control sample.